JPH04112232U - camera photometry device - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the storage capacity and photometry time in a photometry device that obtains the average received light data value from the periodically changing amount of received light. [Configuration] A light receiving element 1 that outputs an electrical signal according to the amount of received light, and a timer counter 51 that measures a certain amount of time.
and photometry means 2 and 3 that sample the output of the light receiving element 1 multiple times within the predetermined time and convert it into digital data.
and two storage means 53A for storing digital data,
53B, and the sampled digital data are compared with the data stored in the storage means 53A and 53B, and the larger and smaller data are stored in the respective storage means, and after the predetermined period of time has elapsed, each storage means and a calculation unit 53 that calculates the average of the maximum value and minimum value stored in and outputs it as a photometric value.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention relates to a camera exposure control device, which is especially necessary when determining exposure. The present invention relates to a photometry device for measuring the brightness of a subject.

0002

[Conventional technology]

Conventionally, a photometry device that is part of a camera's exposure control device measures the brightness of the subject. Photometry is performed using a light-receiving element whose output changes depending on the intensity of the light. in this case, Flicker light that changes in brightness at a certain period, such as electric lights that use alternating current. In this case, sampling is performed multiple times within a certain period of time, and the average of these sampling values is By calculating the value, the photometric data value is obtained, and exposure control is performed based on this data value. Is going.

0003 For this reason, conventional photometric devices require a memory for storing multiple sampling values. device and each sampling value stored in this storage device is added and divided. An arithmetic circuit is provided. In this case, each sampling value is stored in a storage device, And in order to read this, a CPU and address decoder are required to control these. Needless to say, there will be other restrictions.

0004

[Problem that the idea aims to solve]

In this way, with conventional photometry devices, it is difficult to store multiple sampling values once. A storage device is required, but in order to perform high-precision photometry, one cycle of flickering light is Since a sampling number of at least 50 is required for the In order to temporarily store sampling values, a storage capacity of at least 50 or more is required. Therefore, a storage device with a large capacity is required. Also, with the increase in the capacity of storage devices, Therefore, the circuits to control these elements become complicated, and the system of photometering equipment becomes difficult. The problem is that the system becomes more complex. In addition, processing is performed to process large amounts of data. This increases the time and becomes an obstacle to shortening the photometry time. The purpose of this invention is to create a storage device with an extremely small capacity that can perform suitable photometry in a short period of time. An object of the present invention is to provide a photometry device for a camera that makes it possible to perform photometry.

[0005]

[Means to solve the problem]

The photometric device of this invention consists of a light receiving element that outputs an electrical signal according to the amount of light received, and a constant a timer that measures the time, and samples the output of the light receiving element multiple times within this fixed time. A photometric means that outputs digital photometric data by ringing, and a photometric device that outputs digital photometric data. Two storage means for storing data and one for recording sampled photometric data in the storage means respectively. Compare the stored data and store the larger and smaller data in the respective storage means. The maximum and minimum values stored in each storage means are stored after the specified period of time has elapsed. and calculation means for calculating the average of the values and outputting it as a photometric value. Here, the photometric means can be composed of a photometric circuit and an A/D conversion circuit. or, The timekeeping means, the storage means, and the calculation means are provided in the microcomputer, and especially the timekeeping means is The time means is configured as a timer counter, and the storage means and calculation means are configured as a calculation section. can be done.

[0006]

【Example】

Next, the present invention will be explained with reference to the drawings. Figure 1 shows the structure of one embodiment of the present invention. FIG. In the figure, 1 indicates that the electrical output changes depending on the amount of light received. A light-receiving element consisting of a photoelectric conversion element such as a photodiode or phototransistor The electrical output is amplified in the photometric circuit 2 and output as photometric data. It will be done. This photometric data is converted into a digital value by the A/D conversion circuit 3, and then It is input into the computer 5. This microcomputer 5 includes an exposure control device. , photometry switch 6, release switch 7, power supply 8 and transistor 9 are connected. The base potential of the transistor 9 is controlled based on the state of the photometric switch 6. By doing so, the power source is connected to the light receiving element 1, the photometry circuit 2, the A/D conversion circuit 3, and the exposure control device. After connecting to the device 4, start photometry operation. Also, release switch 7 was turned on. Sometimes, the exposure control device 4 is controlled based on photometric data.

[0007] The microcomputer 5 includes a timer that measures a certain period of time from the time of reset. A counter 51 and a control unit that operates based on the clock output of the timer counter 51. 52, and an arithmetic unit 53 operated in a predetermined sequence by the control unit 52. It is growing. This calculation section 53 includes a calculation circuit that performs necessary calculations, as well as photometric data. It is equipped with memories 53A and 53B that can store the maximum and minimum values of A/D. The photometric data input from the conversion circuit 3 and the data stored in the memories 53A and 53B are The larger or smaller data is stored in the memories 53B and 5, respectively. Store it in 3A. Also, after a certain period of time has elapsed, the information is stored in the memories 53A and 53B, respectively. The average value of the maximum value and minimum value data is calculated, and this average value is applied to the exposure control device 4. It is configured to output to.

[0008] The operation of the photometric device having this configuration will be explained using the flowchart of FIG. First of all, When the photometry switch is turned on and the signal P1 is input to the microcomputer 5 ( In step 11), the microcomputer 5 transfers the signal P3 to the base of the transistor 9. , and turns on transistor 9 to transmit light receiving element 1, photometry circuit 2, and A/D conversion. Connect the power supply 8 to the circuit 3 and the exposure control device 4 and put them into operation (step 12) . Also, at the same time, the timer counter 51 is reset to start counting a certain period of time. Then input 00 (H), the minimum value of hexadecimal data, into the maximum value memory 53A. , input FF(H), which is the maximum value of hexadecimal data, into the minimum value memory 53B, and is stored (step 13).

[0009] Then, the light receiving element 1 starts receiving light, and the photometry circuit 2 and A/D conversion circuit 3 are activated. Through this, photometric data corresponding to the amount of received light is sequentially input to the microcomputer 5. (Step 14). Then, the calculation section 53 of the microcomputer 5 calculates the input The photometric data stored in the memory 53A and 53B are sequentially compared with the data stored in the memories 53A and 53B. , the larger one is stored in the memory 53A, and the smaller one is stored in the memory 53B (step 15-18). This continues until the fixed time of the timer counter 51 has elapsed. Ru. As a result, the maximum value of the photometric data up to that point is sequentially stored in the memories 53A and 53B. The minimum value is stored while being updated. When a certain period of time has passed (step 19), The calculation unit 53 takes out the data stored in the memories 53A and 53B, respectively, and The average value of both is calculated (step 20). In this calculation, each memory 53 There are two calculations: one to find the sum of the data of A and 53B, and one to find the quotient by dividing the sum by 2. In particular, in this case, in operations using binary numbers, each memory 53A, 53B is The quotient is rounded off by adding 1 to the sum of the data and shifting the digit down one place. can be easily obtained. The obtained average value is output to the exposure control device 4, where it is A predetermined exposure calculation process is performed (step 21).

0010 After that, if the metering switch is still on, the timer counter will start again. The controller 51 is operated to maintain that state for a predetermined period of time (steps 22 to 25). Before the time elapses, the release switch 7 is turned on and the signal P2 is output to the microcomputer. When the signal is input to the computer 5, it outputs a signal to the exposure control device 4 and controls the exposure in the previous process. Exposure control is performed based on the processed data (steps 26 and 27). If the release switch 7 is not turned on before the time elapses, the signal P3 is activated. Turn off the detector 9 and disconnect the power source 8 from the light receiving element 1 etc. (step 28).

Therefore, as shown in FIG. 3, the set time t of the timer counter 51 is set slightly longer than the period of the flickering light received by the light receiving element 1, and a sufficient number N of samples are sampled within this set time t. The microcomputer 5 calculates the maximum and minimum values of the photometric data obtained by performing the above steps, and calculates the average of these maximum and minimum values to obtain the average amount of flicker light. In FIG. 3, nine samplings are performed, and the average value of the maximum value a ₃ and minimum value a ₆ of the obtained data a ₁ to a ₉ is calculated. Even if the average value is obtained from the maximum and minimum values of the photometric data, if the light intensity changes periodically, such as with flickering light, it is necessary to calculate the total average of the photometric data obtained through multiple samplings. Since it is possible to obtain substantially the same photometric data value as in the case where the photometric data value is the same, there is almost no error or decrease in accuracy in the photometric data value. Further, it is preferable that the number of samplings N be 50 or more.

0012 In this way, even if the number of samples is set to an extremely large number, In the calculation unit 53 of the computer 5, the photometric data inputted sequentially and the memory 5 are processed. After comparing the data stored in 3A and 53B, the larger and smaller You only need to rewrite the data in one memory to memories 53A and 53B, so there are only two memories. That's fine. Therefore, it is desirable to reduce the number of memories and simplify the configuration of the photometric device. At the same time, the circuit for controlling the memory is simplified, making it easy to configure the photometry device. It becomes possible to do so. Moreover, all you need to do is calculate the sum and quotient of two data. Therefore, it is also possible to shorten the photometry time by shortening the calculation time.

[0013]

[Effect of the idea]

As explained above, the present invention sequentially collects photometric data sampled over a certain period of time. Compare the data stored in the next two memories and compare the larger and smaller data. The maximum value of the data stored in memory after a certain period of time has passed. Since the average value of photometric data is obtained based on the average value of the minimum value, please note at least two notes. It is possible to obtain the average value of photometric data using Therefore, the configuration of the photometric device can be simplified. Also, when calculating, 2 Since only the calculation process of finding the sum and quotient of two data is required, the calculation process is reduced and the photometry Time can be shortened.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the present invention.

FIG. 3 is a diagram showing photometric data and its sampling state for explaining the operation of the present invention.

[Explanation of symbols]

1 Light receiving element 2 Photometry circuit 3 A/D conversion circuit 4 Exposure control device 5 Microcomputer 51 Timer counter 52 Control section 53 Arithmetic unit 53A, 53B memory 6 Photometry switch 7 Release switch 8 Power supply 9 transistor

Claims (1)

[Scope of utility model registration request] 1. A light-receiving element that outputs an electrical signal according to the amount of received light, a timer that measures a certain amount of time, and an output of the light-receiving element that is sampled multiple times within the certain period of time to produce digital photometric data. A photometric means for outputting, two storage means for storing digital data, and comparing the sampled photometric data with the data respectively stored in the storage means, and storing the larger and smaller data in the respective storage means. A photometry device for a camera, characterized in that the photometry device for a camera is provided with a calculation means for calculating the average of the maximum value and the minimum value stored in each storage means and outputting it as a photometry value after the elapse of the predetermined period of time.